Successive approximation digital voltage regulation methods, devices and systems

1. A low power voltage regulator, comprising:

a weighted transistor array having a plurality of transistor switches with a total conductance of G, the switches corresponding to bits ranging from a most significant bit (MSB) to a least significant bit (LSB), a transistor switch corresponding to the MSB having a conductance of G/2 and remaining bits having a consecutive descending conductance of G/2 N to the LSB, and further including a redundant LSB transistor switch having the same G/2 N conductance of the LSB;

a search controller that conducts a binary search by turning on respective ones of the plurality of transistor switches beginning with the MSB to find a total conductance value of said weighed transistor array that realizes the nearest output voltage to a desired target output voltage;

a LSB controller to enable the redundant LSB transistor in response to steady-state errors;

an overshoot controller that interrupts the search controller in response to voltage or current step changes that are large enough to cause predetermined amounts of overshoot or undershoot; and

a proportional derivative controller to compensate an output voltage from the weighted transistor array.

2. The regulator of claim 1 , wherein the search controller conducts a recursive successive approximation by turning on bits from the MSB to the LSB for coarse control within a coarse range of the target voltage and then the overshoot controller conducts fine control after the coarse control determines a predetermined number of MSB bits to turn on to achieve the coarse range.

3. The regulator of claim 2 , wherein the overshoot controller comprises a hysteretic dual-bound bang-bang controller.

4. The regulator of claim 3 , wherein the hysteretic dual-bound bang-bang controller resets the search controller to conduct coarse control if the output voltage falls out of a regulation boundary.

5. The regulator of claim 3 , wherein the hysteretic dual-bound bang-bang controller controls the binary search to a fraction of the LSB.

6. The regulator of claim 1 , wherein the proportional derivative controller cancels an output pole to provide a single pole voltage output.

7. The regulator of claim 6 , wherein the proportional derivative controller comprises two pulse width modulation comparators that implement a proportional term, a comparator to implement a differential term, and a replica path to reject charge injection and kickback.

8. A method for proportional derivative digital compensation of a voltage regulator, the method comprising generating an output voltage in a voltage regulator targeting a target voltage and eliminating an output pole of the voltage regulator to provide a stable voltage regulator operation irrespective of load current, load capacitance, or sampling frequency.

9. The method of claim 8 , wherein the eliminating the output pole avoids oscillatory behavior in response to the slope of the output achieving a correct polarity by discontinuing output approximation and allowing the compensation to stabilize the output voltage.

10. A method for duty cycle regulation of a digital voltage regulator, the method comprising generating an output voltage in a voltage regulator targeting a target voltage with a plurality of bits from a most significant bit to a least significant bit, and adding additional effective number of to increase a resolution limit of the digital voltage regulator by regulating voltage below the least significant bit of the digital voltage regulator through pulse-width-modulation of an additional LSB (least significant bit) switch.